先安装 setuptools:
进入setuptools 文件夹，运行：python setup.py install
再安装 pip：
进入 pip 文件夹，运行：python setup.py install
若未安装 setuptools，直接安装 pip，则会出现以下错误：
ssl_.py:122: InsecurePlatformWarning: A true SSLContext object is not available. This prevents urllib3 from configuring SSL appropriately and may cause certain SSL connections to fail.
